1. Field of the Invention
This invention relates primarily to processes classified in Class 166 of the United States Patent Office, and more particularly to the production of earth fluids by displacement fluids.
2. Description of the Prior Art
U.S. Pat. No. 3,482,631 teaches injecting an aqueous preslug containing a viscosity imparting agent, e.g., high molecular weight polymers such as partially hydrolyzed polyacrylamides, biopolymers, e.g., polysaccharides, and other similar materials, and electrolyte and/or semipolar organic compounds.
U.S. Pat. No. 3,324,944 teaches injecting a nonpolar organic liquid preslug, e.g., hydrocarbons that are fluid under formation conditions, preferably with a viscosity about that of the crude (low viscosity hydrocarbons such as propane, butane, and straight run gasoline, thickened by agents such as polyisobutylenes) into the formation to improve the stability of subsequent microemulsion injection into the formation.
U.S. Pat. No. 3,343,597 teaches injecting an aqueous slug of controlled ion content into the formation prior to the injection of the micellar dispersion. The micellar system is thus protected from ions in formation water during the secondary type oil recover.
U.S. Pat. No. 3,698,479 teaches injecting oil external micellar solution which comprises in part a cosurfactant such as ethylene oxide. The viscosity of the slug increases from its leading edge to its trailing edge.
U.S. Pat. No. 3,692,113 teaches use of polyalkene oxide polymer solutions with added metal ions to provide increased flow resistance.